It is interested in examining treatment effect on a particular category of subjects or in comparing treatment effects among different subgroups as well as overall treatment effect due to heterogeneity of study subjects. Subgroup analyses are exceedingly common, but they are also often misleading. Conclusions based on subgroup analyses can do harm both when a particular category of people is denied effective treatment (a "false-negative" conclusion), and when ineffective or even harmful treatment is given to a subgroup of people (a "false-positive" conclusion). Because of the frequency and the importance of clinical application of subgroup analysis, researchers need to be cautious about doing subgroup analyses. This study presents guidelines to help conducting subgroup analyses correctly.
Population Characteristics

Confounding is the distortion of a disease/exposure association brought about by other factors which are not considered in the study design or the data analysis. These factors are called confounding factors. We should be cautious in data analysis of observational study of association of disease/exposure, since confounding often occurred in observational study. This study examines confounding effect according to data pattern (the ratio of controls to cases, the ratio of exposures to non-exposures for each level of confounding factor), criteria for treating a variable as a confounding variable, and some notes for the analysis in case-control study.
Case-Control Studies* ; Confounding Factors (Epidemiology) ; Observational Study ; Statistics as Topic

Objectives: The Panbio COVID-19 Ag Rapid Test Device (Panbio COVID-19 Ag, Abbott Rapid Diagnostics) is a lateral flow immunochromatographic assay targeting the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleoprotein in nasopharyngeal specimens for the diagnosis of coronavirus disease 2019 (COVID-19). This study aimed to verify the performance of the Panbio COVID-19 Ag for implementation in clinical laboratories. Methods: Sixty nasopharyngeal swab specimens (30 positive and 30 negative) dipped in transport medium, and COVID-19 was confirmed using real-time RT-PCR using Allplex SARS-CoV-2 assay (Seegene), were tested using the Panbio COVID-19 Ag. Reproducibility was evaluated using positive and negative control materials. Sensitivity and specificity were calculated based on the results of realtime RT-PCR as the standard test method. Results: Reproducibility was confirmed by the consistent results of repeated tests of the quality control materials. The overall sensitivity and specificity of Panbio COVID-19 Ag were 50.0% and 100.0%, respectively. Panbio COVID-19 Ag demonstrated high sensitivity (88.2%) in analyzing the detection limit cycle threshold (Ct) value of 26.67 provided by the manufacturer as a positive criterion, and the sensitivity was 100.0% for the positive criterion of Ct values <25, although it was less sensitive for Ct ≥ 25. Conclusion Considering the high sensitivity for positive samples with Ct values <25 and the rapid turnaround of results, Panbio COVID-19 Ag can be used in clinical laboratories to diagnose COVID-19 in limited settings.

OBJECTIVE: The aim of this study is to investigate the effects of cooperative training on the pretreatment assessment of the feasibility to perform Ultrasonography (US) guided percutaneous radiofrequency ablation for patients afflicted with hepatocellular carcinoma. MATERIALS AND METHODS: In our prospective study, 146 patients with 200 hepatocellular carcinomas were referred for radiofrequency ablation after triage by hepatologists. Three radiologists with different levels of experience performed the planning US before (group I) and after (group II) cooperative training, to evaluate whether radiofrequency ablation was feasible. The feasibility rates considered eligible according to our criteria were evaluated. In addition, we analyzed the reasons for the lack of feasibility were analyzed. The interobserver agreement for the assessment of feasibility before and after training was also calculated. RESULTS: The overall feasibility rates for both groups was 73%. No significant difference in the feasibility rates was observed. The feasibility rates of each observer for group I were 71% (observer 1), 77% (observer 2) and 70% (observer 3) and those for group II were 73%, 76% and 69%, respectively. In the tumors (n = 164) considered ineligible, the two most common causes for refraining from performing radiofrequency ablation included non-visualization of the tumor (62%) and the absence of a safe route for the percutaneous approach (38%). We found moderate interobserver agreement for all observers before cooperative training and a good agreement after training. CONCLUSION: Although the cooperative training did not affect the feasibility rate of each observer, it improved the interobserver agreement for assessing the feasibility of performing US guided radiofrequency ablation, which may reduce unnecessary admission or delayed treatment.
Adult ; Aged ; Aged, 80 and over ; Carcinoma, Hepatocellular/*surgery/ultrasonography ; *Catheter Ablation ; Clinical Competence ; Feasibility Studies ; Humans ; Inservice Training ; Liver Neoplasms/*surgery/ultrasonography ; Male ; Middle Aged ; Prospective Studies ; Reproducibility of Results ; *Ultrasonography, Interventional

Objectives: ：The high lifetime prevalence of depression in Korea is related to problems such as suicide and decreased productivity, as well as the cost of disease due to increased use of medical services, which can cause great socioeconomic loss. Therefore, in this study, the burden of disease of depression and the importance of managing mental health diseases, which are increasing day by day, are suggested to be helpful in determining priorities in health policy establishment. Methods: ：In this study, the socio-economic cost of depression was calculated by dividing it into direct cost and indirect cost. For statistical data, data from the National Health Insurance Service of the public and statistics on diseases of national interest were mainly used. Results: ：As a result, the socio-economic cost of depression in 2019 estimated in this study was calculated to be a total of KRW 4.83 trillion, with direct costs 692.9 billion won and indirect costs 4.13 trillion won. Among them, the cost due to decrease in work performance accounted for the largest portion, accounting for 65.5%. Conclusions ：As the socio-economic burden due to depression is expected to increase in the future, it is necessary to establish a systematic funding plan for the treatment and management of depressed patients in daily life.

Background: and PurposeSleep disturbance is common in patients with primary headache disorders. We were interest in whether poor sleep quality affects patients directly or via increases in the frequency and severity of headaches. To that end, we investigated the direct and indirect effects of sleep quality on the headache-related impact among patients with primary headache disorders. Methods: We analyzed migraine and tension-type headache (TTH) in patients included in the headache registry of our headache clinic from October 2015 to May 2018. We collected information on the headache frequency, severity, and psychological status. Sleep quality and headache-related impact were measured using the Pittsburgh Sleep Quality Index and Headache Impact Test-6, respectively. We performed path analyses with headache frequency and severity as covariates to determine the direct effect of sleep quality on the headache-related impact, and the indirect effects mediated by increases in the headache frequency and severity. Results: This study included 915 patients: 784 with migraine and 131 with TTH. Worse sleep quality was independently associated with greater headache-related impact in both patients with migraine and those with TTH. Path analysis revealed a direct effect (β=0.207,p<0.001) of sleep quality and an indirect effect mediated by headache frequency and severity (β=0.067, p=0.004) on the headache-related impact in migraine. In TTH, only direct effects of sleep quality on the headache-related impact were significant (β=0.224, p=0.004). Conclusions We suggest that poor sleep quality can directly increase the headache-related impact in both patients with migraine and TTH as well as indirectly by increasing the headache frequency and severity in patients with migraine.

BACKGROUND AND OBJECTIVE: The aging process affects the responsiveness and other functions of endothelium and vascular smooth muscle cells, predisposing the old vessels to the development of atherosclerotic lesions. Endothelial nitric oxide synthase (ecNOS) gene polymorphism was shown to affect the occurrence of acute myocardial infarction (AMI). We hypothesized that aging may affect the association between the ecNOS gene polymorphism and AMI. METHODS: We investigated the age-related distribution of the ecNOS gene a/b polymorphism in 121 male AMI patients and 206 age-matched healthy male controls. As a control, we also genotyped b-fibrinogen gene H1/H2 polymorphism in the same population. RESULTS: The aa, ab, and bb genotypes were found in 1, 49 and 156 cases among the control subjects and 5, 23 and 93 cases among the AMI patients, respectively. There was a significant association between the ecNOS polymorphism and AMI (p=0.045). When the correlation was analyzed by age, the significance remained only in the group below the age of 51 (p=0.009). The distribution of the b-fibrinogen gene H1/H2 alleles, however, was not found to be associated with development of AMI in both young (p=0.7400) and old (p=0.2160) population. CONCLUSION: Our results provide the first evidence that links ecNOS polymorphism to the risk of AMI in relation to age. Young persons who smoke or have ecNOS aa genotype may have an increased risk of developing AMI. The functional as well as structural changes associated with aging in the vascular endothelium may mask the effect of the ecNOS polymorphism in the development of AMI in old people.
Aging ; Alleles ; Endothelium ; Endothelium, Vascular ; Genotype ; Humans ; Male ; Masks ; Muscle, Smooth, Vascular ; Myocardial Infarction* ; Nitric Oxide Synthase ; Nitric Oxide Synthase Type III* ; Smoke ; Smoking

Inflammation and activation of immune cells have important roles in the pathogenesis of atherosclerosis. We analyzed the plasma levels of inflammatory markers and the degree of activation of peripheral blood monocytes and T-lymphocytes isolated from 12 unstable angina, 12 stable angina, and 12 normal subjects. In 20%-33% of patients, monocytes expressed high basal levels of IL-8, tissue factor, IL-1beta, and monocyte chemoattractant protein-1 mRNA. Furthermore, basal mRNA levels of these cytokines showed strong correlation with each other (p < 0.01 in all combination) but not with tumor necrosis factor-alpha or transforming growth factor-beta1. Plasma level of C-reactive protein was highest in the unstable angina patients (1.63+/-0.70 mg/l) and lowest in the control subjects (0.22+/-0.08 mg/l) (P = 0.03). We also observed a high correlation between C-reactive protein level and the occurrence of minor and major coronary events during 6 months of follow-up. Activation status of T-cells, assessed by the percentage of HLA-DR positive cells, was highest in the unstable angina patients (26.8+/-1.4%) compared with that in the control (14.7+/-1.2%) (P = 0.0053). Our data represent the first case showing that the circulating monocytes in angina patients are activated to a state express numerous proatherogenic cytokines. These results may help to diagnose angina patients according to the inflammatory markers and evaluate the prognosis of the disease.
Aged ; Angina Pectoris/immunology* ; Angina Pectoris/diagnosis ; Angina, Unstable/immunology* ; Angina, Unstable/diagnosis ; Biological Markers/blood ; C-Reactive Protein/analysis ; Cytokines/blood* ; Female ; HLA-DR Antigens/immunology ; Human ; Interleukins/blood ; Lymphocyte Transformation ; Male ; Middle Age ; Monocyte Chemoattractant Protein-1/blood ; Monocytes/metabolism* ; RNA, Messenger/metabolism ; T-Lymphocytes/metabolism* ; Transforming Growth Factor beta/analysis ; Tumor Necrosis Factor/analysis

We aimed to compare the CT findings of nontuberculous mycobacterial pulmonary diseases caused by Mycobacterium avium-intracellulare complex (MAC) and Mycobacterium abscessus. Two chest radiologists analyzed retrospectively the thin-section CT findings of 51 patients with MAC and 36 with M. abscessus infection in terms of patterns and forms of lung lesions. No significant difference was found between MAC and M. abscessus infection in the presence of small nodules, tree-in-bud pattern, and bronchiectasis. However, lobar volume decrease (p=0.001), nodule (p=0.018), airspace consolidation (p=0.047) and thin-walled cavity (p=0.009) were more frequently observed in MAC infection. The upper lobe cavitary form was more frequent in the MAC (19 of 51 patients, 37%) group than M. abscessus (5 of 36, 14%) (p=0.029), whereas the nodular bronchiectatic form was more frequent in the M. abscessus group ([29 of 36, 81%] vs. [27 of 51, 53%] in MAC) (p=0.012). In conclusion, there is considerable overlap in common CT findings of MAC and M. abscessus pulmonary infection; however, lobar volume loss, nodule, airspace consolidation, and thin-walled cavity are more frequently seen in MAC than M. abscessus infection.
Adult ; Aged ; Aged, 80 and over ; Anatomy, Cross-Sectional/methods ; Diagnosis, Differential ; Female ; Humans ; Lung Diseases/*microbiology/*radiography ; Male ; Middle Aged ; Mycobacterium Infections, Atypical/microbiology/radiography ; Mycobacterium avium-intracellulare Infection/microbiology/*radiography ; Research Support, Non-U.S. Gov't ; Retrospective Studies ; Tomography, Spiral Computed/*methods ; Tuberculosis, Pulmonary/radiography

Although several studies examined factors that influence conscious sedation, investigation was limited into the gender and age. The aim of this prospective study is to identify the clinical variables of successful conscious sedation during gastrointestinal endoscopy. A total of 300 subjects who underwent gastrointestinal endoscopy were enrolled in a prospective fashion. They completed a questionnaire to assess height, weight, drinking, smoking, education level, recent medication, past medical history, previous experience of conscious sedation, preprocedural anxiety, and apprehension about the procedure. Efficacy of sedation and amnesia were evaluated by the subject and the endoscopist. Amnesic and sedative effects were proportionally related with age (p<0.0001). Preprocedural anxiety level was higher in women (p=0.0062), younger subjects (p=0.035), slender subjects (p=0.041), and in those without previous experience of conscious sedation (p=0.0034). This anxiety level was also related to increased pain (p=0.0026) and alertness (p=0.0003) during the procedure. Lower dose of midazolam is needed for sedation in older subjects. Subjects with a high level of preprocedural anxiety such as women, younger subjects, slender subjects, and those without previous experience of conscious sedation should be sedated with great caution because generally, they complain of much more severe pain and alertness during the procedure.
Age Factors ; Anesthetics, Intravenous/therapeutic use ; Body Weight ; *Conscious Sedation ; *Endoscopy, Gastrointestinal ; Female ; Humans ; Male ; Midazolam/therapeutic use ; Pain/drug therapy ; Prospective Studies ; Questionnaires ; Treatment Outcome